Various prior art apparatuses have been disclosed which are adapted for holding, cutting and removing tissue from surgical zones, such as the human eye. A number of patents has been issued over the years covering various apparatuses which have sought to automatically (either pneumatically or electrically) control the cutting and suctioning of materials from various surgical zones. In the instances where the surgical zone is the human eye, it is vital that the unwanted material in the eye be severed and removed from the interior sections of the eye without doing damage to the rest of the eye, such as the retina which may result in a detached retina. Damage may result to further interior areas of the eye, such as the choroid which underlies the retina or the optic nerve or the blood vessels associated with the nerve. In order to prevent what may result in a permanent damage to certain portions of the interior eye, it is desirable that during the process of withdrawing or suctioning unwanted materials from the eye's interior, that any significant residue suction on the interior of the eye when the cutting is at rest be eliminated. Thus, it is most desirable that any vacuum or pressure which must be applied to the eye's interior to withdraw unwanted material from the eye only be applied to the eye's interior when material is actually being suctioned from the area.
Of the numerous prior art apparatuses which are known in the industry, perhaps the O'Malley apparatus which is the subject of U.S. Pat. Nos. 3,815,604 and 3,884,238 is perhaps the most well-known. The apparatus is provided with means for severing the unwanted materials from the main sections of the eye and for applying a vacuum to the eye's interior for withdrawing the vitreous material from the eye. An adjustable bleeder valve is provided in the vacuum line to eliminate residue suctioning on the eye's interior when the cutting action is completed, or is otherwise at rest. This apparatus does not provide, nor is there an appreciation for the need for, linearly controlling the suctioning of material from the eye.
A number of additional patents, including U.S. Pat. Nos. 3,589,363; 3,732,858; 3,805,787; 3,812,855; 3,844,272; 3,920,014; 3,937,222; 3,996,935; and 4,007,742 which have been issued to Anton Banko, have disclosed various apparatuses for both severing and removing unwanted material from various surgical zones, such as vitreous material from the human eye. While each of the foregoing patents has involved some means and apparatus with severing and withdrawing materials from the surgical zone, perhaps the most pertinent of the foregoing patents to the present disclosure is U.S. Pat. No. 3,812,855 which discloses a system for controlling pressurized fluid and suction pressure to and from the surgical zone. While the apparatus does have certain automated features, the pressure of the fluid flowing to and from the operating zone is mechanically sensed. Thus, it follows that the response time for correcting an insufficient or an excess amount of pressurized fluid to or from the surgical zone may well not be uniform and, thus, opens the way for damage to the surgical zone, such as the eye when an insufficient or an excess amount of suctioning pressure is applied to the interior of the eye. The '855 apparatus does, however, provide means, such as bleeder valves, for increasing the amount of pressure to or from the eye in response to an insufficient or an excessive pressure reading, respectively.
A further apparatus is disclosed in U.S. Pat. No. 3,902,495 (Weiss). This apparatus makes use of an ultrasonic hand piece for insertion into the eye, together with a fluidic flow system for use in irrigation and aspiration of a small elastic pressure-responsive chamber, such as the human eye during ultrasonic emulsification of a cataract in the eye. The aspiration portion of the apparatus has a withdrawal hose which has a release valve set to open to atmosphere should the pressure differential in the fluidic withdraw hose exceeds a predetermined pressure.
U.S. Pat. No. 3,693,613 (Kelman) teaches a flow control system to be used in conjunction with a surgical hand piece for the removal of unwanted materials from the surgical zone. The apparatus includes both an irrigation and an aspiration subsystem with the aspirating subsystem comprising a prompt use to remove the unwanted material from the zone and to overcome the friction and other losses throughout the entire fluid system. The aspiration subsystem is further provided with a flow transducer to measuring the rate of flow of fluid from the surgical zone and a vent valve to reduce the flow when necessary to assist in maintaining a relatively constant pressure within the operating zone. An electronic flow control receives signals from the flow transducer and reacts to certain changes in flow signals by sending a signal to the venting valve.
As in all aspirating or suctioning systems, it is important that as the target tissue which must be severed and removed from the surgical zone varies, in mobility, texture and accessibility, the suctioning pressure applied to the surgical zone must vary likewise. Thus, it follows that a level of suction which might be suitable for one situation might provoke disaster in another situation particularly when the surgical zone is the human eye. Also, the level of suctioning may not only vary from one human eye to another, but may vary in the same eye depending on the location of the surgery. Consequently, it is highly desirable, technically and therapeutically, that a range of vacuum be selectively and readily available to a surgeon to serve the ever-changing needs which are encountered.
The aforementioned prior art apparatuses have been characterized with a number of problems, such as those which result from manually sensing the pressure along the aspirating conduit such as is the case '855 Banko device. Another problem which is also associated with the manual sensing of the pressure along the aspirating conduit is the obvious delay response time in eliminating the suction force which is applied to the interior of the surgical zone, such as the eye, when the cutting of the vitreous or other unwanted material has ceased. This delay response time may likewise be the result of manually sensing the pressure along the aspirating conduit. Such a delay in responding to the need for more or less suctioning force within the surgical zone can often times result in the damaging disorder known as aphakic-like retina detachment. This retina disorder was also found to be associated with many of the prior art apparatuses which make use of a winding, rotating apparatus for cutting and withdrawing materials from the interior of the human eye.
It was earlier thought that the winding forces of the rotating vitrectomy machines were the only factor in causing retina detachment. But the apparatuses which were disclosed in the O'Malley patent which made use of a reciprocating cutter to eliminate the winding forces, still resulted in a definite incidence of post-operative aphakic-like retina detachment. Thus, the most prevalent problems of the prior art aspirating apparatuses which were the result of an inadequate response time, often times due to manually sensing the pressure along the aspirating conduit, and to the instances of aphakic-like retina detachment which were often times associated with the winding forces of the rotating aspirating apparatuses, remain a part of the piror art aspirating apparatuses for the most part.